1. Field of the Invention
The present invention relates to an encoder dampening mechanism. More specifically, the present invention relates to an encoder dampening mechanism for an electric spot welding gun equipped with a servo motor that is accommodated inside of a motor housing and causes a rotor to rotate, and an encoder that detects a rotation angle of the rotor.
2. Related Art
Conventionally, an electric spot welding gun has been used when overlapping and welding plate materials. Such an electric spot welding gun is equipped with a pair of electrode tips disposed to sandwich welding target members. From among the pair of electrode tips, one electrode tip is fixed, and the other electrode tip is made to abut the welding target members, so as to perform spot welding.
In addition, such an electric spot welding gun includes a motor housing that forms a main body, a servo motor that is accommodated in this motor housing, and an encoder that detects the rotation angle of a rotor applying torque on a feed screw mechanism of this servo motor. The welding gun plots the position of the other electrode tip based on the rotation angle of the rotor detected by the encoder and the pitch of a feed screw mechanism, and causes the other electrode tip to abut the welding target member.
Incidentally, shock in the axial direction of the rotor may act on this rotor of the servo motor via the feed screw mechanism when such an electric spot welding gun is plotting the position of the other electrode tip and causing it to abut the welding target member.
In this case, if the encoder is directly connected in the axial direction of the rotor, the shock acting in the axial direction via the rotor will inflict damage on the internal components of the encoder. This encoder has thus been the cause of malfunctions.
In light of this, an encoder dampening mechanism for an electric spot welding gun has been illustrated in Japanese Unexamined Patent Application Publication No. H11-197843 in which an input shaft of the encoder is coupled, via a cushion member that absorbs axial shock acting thereon via a rotor of a servo motor, to this rotor. According to this dampening mechanism, shock in the axial direction acting via the rotor can be absorbed by the cushion member.